Heatburst!

Early Thursday morning, residents of Cozad, Nebraska were awakened by a sound that sounded like a tornado. Winds rose to 75 mph. But no thunderstorm was occurring. In minutes, the temperature soared twenty degrees to 91F. Numerous trees fell on houses.

The damage was caused by a heatburst. This unusual weather phenomenon is characterized by intense winds, a dramatic rise in temperature and a desiccating drop in relative humidity. They usually occur late at night into the early morning hours.

There have been several heatbursts this year in the Plains states. On June 16th, a major one hit the area around Midland, Texas. At 11:25 p.m, winds gusted to 62 mph and the temperature rose from 71F to 97F. The observing location was not even in the core of the downburst, and winds were estimated to have been as high as 100 mph.

At Emporia, Kansas on May 25th, the temperature rose from 71F to 91F in 27 minutes between 4:44 a.m. and 5:11 a.m. during a heatburst.

The tiny town of Kopperl, Texas experienced a severe heatburst on June 15, 1960. Winds of 75 mph slammed into the ground and fanned out, sending temperatures soaring. Unofficial readings reportedly were that temperatures briefly reached 140F. Vegetation reportedly looked as if it had been seared by the heat.

Heatbursts are poorly understood. But they apparently occur when evaporating rain in a dying thunderstorm cools dry air aloft, causing it to become dense and heavier. It falls toward the ground at a high velocity. As it descends, it heats by compression and dries. The result is the high winds, rapid temperature increase and moisture drop.

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